Loud speaker adapted for automobile use



Feb. 9, 1932. J. D. sEABERT 1,844,802

` LOUD SPEAKER ADAPTED FOR AUTOMOBILE USE Filed Dec. 15, 1930 BY John D.' -Seaber 2% ATTORNEYS Patented Feb. 9, 1932 UNITED STATES PATENT OFFICE JOHN D. SEABERT, OF DAYTON, OHIO, ASSIGNOR TO GENERAL MOTORS RADIO RPORA- TION, OF DAYTON, OHIO, A. CORPORATION F OHIO LOUD SPEAKER ADAPTED FOR AUTOMOBILE USE Application led December 15, 1930. Serial No. 502,453.

This invention relates to acoustical devices such as are adaptable for use with radio receiving instruments.

One of the objects of the invention 1s to 5 provide a loud speaker, or an acoustical device, that is adapted to be mounted 1n the roof structure of an automotive vehicle without alteration of said roof structure, and without materially disturbing the continulty o of surface of the roof lining or upholstering.

A further object of the instant invention is to provide acoustical devices of the dynamlcal type that are adaptable for automotive use.

A further object of the invention is to provide acoustical devices of the class described having means for baling or dampmg the sound vibrations through an effective 1ncreasev in air path, whereby undesirable reverberations may be eliminated.

' Further objects and advantages ofV the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of one form of the present invention is clearly shown.

In the drawings:

Fig. 1 represents a front view of an acoustic device, part of which is broken away to show the device in section, substantially on the line and in the direction of the arrows 1-1 of Fig. 2.

Fig. 2 is a sectional view, taken on the line and .in the direction of the arrows 2-2 of Fi 1.

lgteferring to the drawings, and particularly to Fig. 2, a main supporting disc or back plate 20 has attached thereto a cup-shaped field housing 22, by a central pole piece 24 and a reenforcing plate 26. A reduced portion 30 of the central pole piece or core 24 projects through apertures of the base 28 of the field housing 22, the supporting plate 2() and the reenforcing plate 26 Vand is there riveted or peened over as illustrated, thus securing these four members in position. This structure is adapted to increase the permeability of the base 28 of the field housing 22, thou h it could be accomplished in any other 50 suita le and well known manner. An annular pole piece 32, attached to the field housing 22 in any suitable manner, carries a reenforcing ring 34, concentrating the flux density across the air gap 33, between it and the pole piece 24.

A field coil 36, having two terminals 38 and 40, connected either to a source of direct current or to a source of rectified current, in order to excite the magnetic field, is disposed within the cup 22 and about the center pole piece 24. Interposed between the field coil 36 and the annular pole ieee 32 there is a spacer 42 of any soft pac ing material that prevents axial movement of the field coil 36, along the core 24.

A reentrant diaphragm 44, that includes a pair of frusto conical surfaces 43 and 45, is firmly secured to a hinge or portion 46 con# stituting a cloth or other flexible ring. This may be accomplished by means of glue 0r any other suitable binding material applied to their overlapping edges as at 48. The cloth ring 46 is clamped at its outer periphery between two rings 50 and 52, of U-shaped or any other form which guarantees rigidity or great firmness. Screws 54, will accomplish this end, and are threaded into one end of a post 56, the other end of which is riveted or otherwise secured to the supporting disc or plate 20 as at 57. At the center of the diaphragm 44, a cylindrical support 58 is attached, upon which is wound a speech coil 60 having appropriate leads 59 and 61.

In order to properly center the cylindrical support 58 with respect to the pole piece 24 and the air gap 33, a spider 64 is cemented or otherwise attached to the diaphragm 44 as at 63, and thence fastened to a reduced portion 65 of the pole piece 24 by a screw 66. The spider 64 being very fiexible allows axial movement of the cylindrical support and the speech coil, but at the same time prevents any radial movement thereof.

A metal supporting ring 68, located between the posts 56 and supported by the U- shaped ring 52, aids to support a sound absorbing ring member 70. The ring is of suitable pressed fibrous material as excelsior, felt or the like which is located within and substantially fills the space between the posts 56 and the cup 22. The ring member 70 prevents free flow of air from one side of the diaphragm 44 to the other side, but guarantees sufficient leakage therethrough to com-Y pensate for the differences in the air pressure before and behind the vibrating diaphragm 44 at vany instant. This ring member 70 acts also like a baffle which increases in effect at the porous mat'erial'of the ring member 7()n tend to reduce or dampen out vundesired reverberations, prominent in a shallow type reproducer as illustrated. However, the p rous vbaille is equally applicable to the conventional form of speaker, in whatever instance its use is deemed necessary or advisable. 'l

A cover-plate or grille 72 of suitabl or desired shape, is providedwi-th several sound openings 74, to allow su'fhcient air to flow through, and is supported by the studs 76, riveted or otherwise secured at 78'to the supporting plate 20,- screws 80 threaded into the said studs securing .the grille in place. Q The unit thus constructed isr adapted to be mounted upon the roof structure of an automotive vehicle without alteration of either the unit or the roof structure. This is f ecomplish'ed by means of screws 82 driven through the back-plate Q0 of the unit into the bowor batton 83 of the ltop structure, thus disposing the lback plate- 20 with its dished portion supporting-the motor within the space between twoadjacent bows `8B, substantially as illus-- trated in Fig. 2'. The unit may be attached to the top before the grille 72 is attached, or thc-grille may be. prof. ded with apertures 84 opposite the 'screws 82 through which access may be had by a suitable tool for driving the screws 82;A

The roof structure has been shown only in fragmentary section, but it is readilyseen that the fabric 85 of the top upholstery,- or the lining as it is known, readily lgives bef tween the bows 83 so 'as to allow disposition of the unit therein. That is Vto say, in mount# ing the unit on the top the bows 83 are located and thence the unit is pressed up against them so as to allow driving of the screws 82, which positioning` of the'unit will stretchthc fabricSsuicient-ly to allow the` unit to be mountedV as' stated. A fterthe unit is thus mounted' the leads 38, e0, 59 and Sil are appropriately connected with the instrument and electrical sources withwhich they are designed for operation, and the installation is then complete. This mounting of the speaker unit offers little or no obstruction to theinner contour ofthe structure, and is not'conspicuous in its appearancesince the face plate 72 lies close against the innersurface of the top and it may be finished in'tone. or color to match with the interior finishing of the Vvehicle.

Vhile the form of embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims .which follow.

lilhat is claimed is as follows Vl. An acoustical device of the class described, comprising in combination; a back platesupportinga motorat its center; a foraminous face plate secured at its periphery to the yback plate;`supporting studs for the face plateand spacingit from said back plate so as to substantially enclose the acoustical device, Va reentrant diaphragm supported on the back member and being disposed concentric with said motor, and apad of-soundabsorbing material secured against saidback member and disposed about said motor.- f 2. An acoustical device comprisingin coin-y bination a supporting plate having a driving motor centrally secured thereof; a diaE phragm secured at its periph-ery to the back plate; and meansA spacing the diaphragm therefrom to provide air passage from one side of the diaphragm to the other; a pad of sound dampening material disposed in the space between the diaphragm andback plate to prevent Afree air flows. from behind the diaphragm; and a-face platezsecuredto the backy member enclosing the diaphragm and motor. j

3. An acousticalY Vdevice comprising/,in

combination a driving` motor, and means' supporting the same comprising; aback plate; a. diaphragmA secured inV spaced -relation@ to the back plate,Y soas.t0v provide air flow over the edge'of saiddia phragm; sound absorbing niaterialksubstantially filling the space betweenthe diaphragm and back member, butbeingi wholly free ,of engagementuvith said diaphragm; said absorbing material beingrof a fibrous nature to prevent free air flow from behind the diaphragm yet permitting free leakage therethrough.

y el. .An acoustical devicel of ,the class described, comprising in combination, a cupped back plate centrally supporting a driving motor; a reentrant conical diaphragm `secured to the back-plate concentric with the motor and being drivingly connected thereto;

,y 5. In an acousticaljdevice: the combination comprising, a back plate of shallow cup formation; a driving motor secured centrally of the plate; said plate providing concentric rows of spaced studs; a diaphragm peripherally secured from one row of studs and being centrally supported with respect to said motor; a grille secured to others of said stud substantially enclosing said motor and diaphragm; and a baille of closely packed ibrous material between the diaphragm and and back plate to effectively increase the air path of vibrations from the rear of the diaphragm.

6. The combination with the roof structure of an automotive vehicle of an acoustic device comprising; a back plate of shallow dished form having flanges; means to secure the plate at its lianges to the bows of said roof structure; a motor carried in the depressed portion of said plate; a reentrant conical diaphragm operatively connected to said motor; spaced studs carried by the back plate supporting the diaphragm at its edges, said studs spacing said diaphragm axially of said plate; fibrous material packed within the space between the diaphragm and the plate; a grille carried by the back member having free air access to both sides of the diaphragm except for the librous material; and means maintaining the said fibrous material from engagement with said diaphragm.

7. In an acoustical device of the electrodynamic type, the combination comprising a support providing a field coil; a reentrant conical diaphragm carried by the support and provided with a voice coil disposed for movement in the air gap of said field coil; studs supporting the diaphragm at its edge, and spacing the same from said support; baille means interposed between the diaphragm and support to restrict free flow of air between alternate sides of the diaphragm, yet permitting free leakage therefrom; and a grille supported from the said plate cooperatting with the same to enclose the elements of said dynamic unit.

8. An acoustical device of the class described, comprising in combination; a back plate supporting a motor at its center; a foraminous face plate secured at its periphery to the back plate; supporting studs for the face plate and spacing it from said back plate so as to substantially enclose the acoustical device; a diaphragm supported at its edge from said back plate; means spacing the diaphragm from both of said plates so as to provide a normally connected air passage between the front and back of said diaphragm about the edge thereof; and a pad of sound absorbing material secured against said back plate and substantially filling the space between the diaphragm edge and the back plate. y

9. An acoustical device of the class described, comprising in combination; a back plate supporting a motor at its center; a foraminous face plate secured at its periphery to the back plate; supporting studs for the face plate and spacing it from said back plate so as to substantially enclose the acoustical. device; means provided by the back plate for securing the device to the roof structure of an automotive vehicle; and means provided by the face plate giving access to the securing means, without disturbance of the contributing parts ofthe device as assembled.

10. An acoustical device for automotive vehicles, comprising in combination; a pair of dished plates forming an enclosure for said device; studs located at the edge of one of said plates, securing them together; a diaphragm interposed between the plates, with means spacing it from each plat-e to provide an air passage about the diaphragm edge and between it and each of said plates; supporting studs spaced about the edge of said diaphragm securing the same to one of said plates; a motor drivingly associated with said diaphragm; and sound absorbing material packed in the space between the diaphragm and its supporting plate to restrict the air flow about the edge of said diaphragm.

In testimony whereof I hereto aiiix my signature.

JOHN D. SEABERT. 

